Ignition circuit radiation suppression structure

ABSTRACT

A wire wound resistor for use in suppressing ignition circuit radiation which has a very low resistance and a specified inductance connected in an ignition circuit close to and in series with the spark plug electrodes, as within the spark plug or between the spark plug lead wire and the spark plug.

United States Patent 1 1 1111 3,883,776

Berry 1*May 13, 1975 [54] IGNITION CIRCUIT RADIATION 3,191,133 6/1965Texsier 315/58 X SUPPRESSION STRUCTURE 3,267,325 8/1966 Why 315/58 X3,771,006 11/1973 Berry 313/118 [76] Inventor: Norman I-I. Berry, 49Cambndge,

Pleasant Ridge, Mich. 48069 FOREIGN PATENTS OR APPLICATIONS =1 NotiCe;The portion of the term of hi 891,357 12/1943 France 313/134 patentSubsequent to No 6 1990 942,973 11 1963 United Kingdom. 313/118 has beendisclaim 898,971 6/1962 United Kingdom .1 338/66 [22] Filed: 1973Primary ExaminerJames W. Lawrence [21] App]. No.: 404,170 AssistantExaminer-E. R. LaRoche Reaed us. Application Data gtctlirraey, Agent, orFlrmWh1ttemore, Hulbert & [63] Continuation-impart of Ser. No. 226,042,Febv 14, p

1972, Pat. No. 3,771,006.

57 ABSTRACT [52] US. Cl. 315/85; 313/118; 313/134; 1

315/58; 315/62; 338/66 A wire wound resistor for use in suppressingignition [51] Int. Cl. I-IOIt 13/04 circuit radiation which has a verylow resistance and a [58] Field of Search 315/41, 54. 57, 58. 62,specified inductance connected in an ignition circuit 315/71, 35;313/118, 134-136; 338/66 close to and in series with the spark plugelectrodes, as within the spark plug or between the spark plug lead [56]References Cited wire and the spark plug.

UNITED STATES PATENTS 6 Cl 3 D F 1,971,497 11/1934 Miller 315/85 x rawmgFIGJ 3040 60 80 I I I I I 200 220240 260280 300 FREQUENCY- MEGAHERTZIGNITION CIRCUIT RADIATION SUPPRESSION STRUCTURE CROSS REFERENCE TORELATED APPLICATIONS This application is a continuation-in-part ofapplication Ser. No. 226,042, filed Feb. 14, I972, now US. Pat. No.3,77l,OO6.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to ignition circuits of the type used on automobiles havinginternal combustion engines and refers more specifically to a wire woundresistor which has a very low resistance and a specified inductancewhich is connected in series with spark plug electrodes so as to beimmediately adjacent the sparking electrodes, which resistor is operableto suppress radiation from the ignition circuit due to sparking of thespark plugs.

2. Description of the Prior Art In the past, suppression of radiationfrom ignition circuits of automobiles on firing of the spark plugstherein has often been accomplished by inclusion of wire wound resistorsin the spark plugs between an upper and lower electrode or connectingsuch resistors in series between a spark plug lead wire and the sparkplug as shown in US. Pat. No. 3,2l2,044 and US. Pat. No. 3,529,273,respectively. Such wire wound resistors of the past have usually been ofrelatively high ohmic value of, for example, 5,000 or [0,000 ohms. Theseprior wire wound resistors have been specified generally by theirresistance value and physical size. Any in ductance in the wire woundresistors has been considered irrelevant in the past. Such resistors arenecessarily wound of fine wire spaced close together so that at theusual ignition circuit voltages flashover between the turns of the wirewound resistors has been a problem limiting the minimum physical size ofthe resistors. A compromise has therefore been reached in the pastbetween the flashover point of the wire wound resistors and the lengthof the resistors and therefore the size of the spark plugs and boots inwhich they have been installed.

SUMMARY OF THE INVENTION It has been found that the inductance of thewire wound resistors is of particular importance in suppression ofradiation from ignition circuits, especially when the wire woundresistors are placed close to sparking electrodes as, for example,within or closely adjacent to the spark plugs of the ignition circuits.On the other hand, it appears that the actual resistance of the wirewound resistors is of little importance in suppressing BRIEF DESCRIPTIONOF THE DRAWINGS FIG. I is a partially broken away view of spark plugconstruction including an ignition circuit radiation suppressionresistor therein constructed in accordance with the invention.

FIG. 2 is a partly broken away view of ignition circuit constructionincluding an ignition circuit radiation suppression resistor constructedin accordance with the invention connected in a boot between a sparkplug lead wire and a terminal adapted to be connected to a spark plug.

FIG. 3 is a graph illustrating ignition circuit radiation suppressionpermissible under the Society of Automotive Engineers recommendationsand that obtained by the resistor of the invention, as illustrated inFIGS. 1 and 2 in three separate installations.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. I, the sparkplug 10 includes an outer metallic body member 12, an inner ceramicinsulating core 14, a pair of lower electrodes 16 and I8 and an upperelectrode 20. The wire wound resistor 22 of the invention iselectrically connected between the lower electrode 16 and the upperelectrode 20 within the insulating core I4 of the spark plug 10 by thesprings 25 and 27.

The spark plug structure 10 as shown is well known and will not beconsidered in detail herein. Further, it is known to place a wire woundresistor 22 between electrodes I6 and 20 to suppress radiation in anignition circuit, in which the spark plug 10 is connected, on sparkingbetween the lower electrodes I6 and 18.

It is also known to place a wire wound radiation suppression resistor 22in an insulating boot construction 34 between a spark plug lead wire 32and an upper spark plug electrode 20. One such boot constructure 34 isillustrated in FIG. 2.

As shown in FIG. 2, the ends of a wire wound radiation suppressionresistor 22 are electrically engaged with the terminals 36 and 38. Theterminal 36 is electrically connected to the spark plug lead wire 32,while the terminal 38 is open to provide a slip fit over an electrode 20ofa spark plug. Inner insulation 40 is provided surrounding theradiation suppression resistor 22, the terminal 36 and a portion of theterminal 38. The outer insulation 42 then encompasses the entirestructure including the inner insulation 40, radiation suppressionresistor 22, terminals 36 and 38 and the end of the spark plug lead wire32 as shown.

Again, it is not new to place radiation suppression resistors in eitherspark plugs or spark plug boot constructions.

However, in the past it has been considered that the wire woundresistors must necessarily be of a resistive value such as 5,000 or10,000 ohms to effectively suppress radiation on sparking between theelectrodes I6 and I8 occurring in an ignition circuit. Accordingly, thewire wound resistors of the past have been so specitied and limited andhave thus been restricted in minimum length due to the possibility offlashover occurring in the wire wound resistors due to the voltageimpressed between the electrodes 20 and I6 and the relatively largeresistance of the wire wound resistors. In the past, the inductance ofthe wire wound resistors has been generally ignored by those interestedin radiation suppression in ignition circuits.

The wire wound resistors 22 in accordance with the invention may besimilar to the usual wire wound resistors in that the wire itself maybe. for example. 0.001 inch or 0.0015 inch in diameter and approximately18 feet long wound on a ceramic core which is, for exam ple. Vs inch tlllo inch in diameter and /8 to /21 inch long. The wire wound resistor22 of the invention. however. differs from the usual wire woundresistors in that the wire wound resistors 22 have very low resistanceas. for example. l to 30 ohms in contrast to the relatively largeresistance of 5,000 to lU.000 ohms of previous wire wound resistors.

In addition, the resistor 22 is designed to have a known inductance as.for example. between ll] and 800 microhenries inductance when calculatedin accor dance with the known formula:

wher

L inductance in ,u h

R radius of the coil N number of turns in the coil 1' length of the coilThe low resistance of the wire wound resistor 22 prevents flashover fromoccurring in the wire wound resis tor even though the resistor may beshorter and have the same number of turns thereon since the voltage dropacross the resistor of between and ohms will be considerably less thanthe voltage drop across the previously used high ohmic value resistors.

Further. the specified inductance of the wire wound resistor 22 which isbetween l0 and 800 microhenries within the scope ofthe invention as setforth above and which is preferably between 30 and microhenries asmeasured on a Tcktronix LC 130 meter. provides the radiation suppressiondesired and previously consid ercd obtainable only with wire woundresistors of higher ohmic \alue. The Tektronix meter is available as anoff-theshelf item from Tektronix in Beaverton, Oregon.

Thus. by providing a wire wound resistor ofpredeten mined inductancerather than predetermined resistance. shorter resistors are possiblewith less chance of a flashover and the resistors may be made of lessexotic alloy wire and will produce equivalent radiation suppression inignition circuits.

The following chart shows actual tests of different wire wound resistorshaving the indicated radiation suppression in standard ignitioncircuits:

Db Attenuation lb lb lil ll ll ll U (i (ill -Continued Db Attenuation5.000 Ohm .l l1 diameter .685 iength 'itlah Further. in FIG. 3 theradiation suppression provided in standard ignition circuits using thelow ohmic value wire wound resistor 22 having an inductance of 30 to 45h. as measured on a Tektroniit LC. I30 meter. as compared against theSociety of Automotive Engi neers recommended standards is presented. Theline 24 shows the Society ofAutomotive Engineers recommended standard,while the lines 26, 28 and 30 illus trate the equivalent resultsobtained by placing wire wound resistors 22 in the spark plugs 10 shownin FIG. 1 in standard ignition circuits.

In the test producing line 28 on the graph of FIG. 3, the ignitioncircuit was a Ford Galaxie 1971. 351 cubic inch combustion engineignition circuit having plain wire plug leads of 39 ohms resistance. Thetest for line 30 on the graph was conducted on a Chrysler horsepower.4cylindcr outboard marine engine as was the test for line 26. Both theChyrslcr engine circuits had 39 ohms resistance in the spark plug lead.in the case of line 30 there was a coiled wire lead while in the case ofline 26 the lead was a plain metallic wire. All ignition circuits had acarbon core lead from the dis tributor to the ignition coil andresistors such as resistor 22 were used in the spark plugs in theignition systems.

From the above indicated results it will be obvious that the lowresistance. specified inductance wire wound resistor 22 ofthe inventionis at least as efficient in suppression of ignition circuit radiation asthe higher resistance resistors thought necessary in the past.

it is hypothesired that the inductance of the resistor 22. especiallywhen place within the spark plug or in the spark plug boot closelyadjacent the sparking electrodes provides a back clectromotive forcewhich tends to dampen oscillations set up in the ignition circuit onsparking of the spark plugs. which oscillations produce the objectionalradiation. The radiation is thus suppressed providing the inductance issufficient even though the resistance value of the resistors 22 isparticularly low.

While one embodiment of the present invention has been considered indetail. it will be understood that other embodiments and modificationsthereof are con templated by the inventor. It is therefore the intentionto include within the scope ofthe invention all embodiments andmodifications as are defined by the ap pended claims.

What I claim as my invention is:

1. An ignition circuit including a spark plug having a pair of lowerspaced apart electrodes. a spark plug lead wire connected in series withthe spaced apart electrodes of the spark plug. and a wire wound ignitioncircuit radiation suppression resistor connected in series with theseries connected spark plug lead wire and electrodes of the spark pingand positioned closely adjacent the electrodes of the spark plug. whichresistor has an inductance of between 10 and 800 microhenries and aresistance of between l5 and 30 ohms.

2. Structure as set forth in claim 1 wherein the spark plug includes anouter metallic body portion. and an inner ceramic insulator corereceived within the outer body portion. and the first of the lowerelectrodes extends through the insulator core, the second of the lowerelectrodes is secured to the outer body portion in spaced relation tothe first lower electrode, and the spark plug further includes an upperelectrode secured to the insulator core in spaced relation to the firstlower electrode and the wire wound radiation suppression resistor ispositioned within the insulator core and connected at opposite ends tothe first lower electrode and to the upper electrode.

3. Structure as set forth in claim 1, wherein an insulating spark plugboot construction is provided between the spark plug lead wire and thespark plug, the wire wound ignition circuit radiation suppressionresistor is positioned within the boot construction which furtherincludes terminals provided within the boot construction for connectingone end of the radiation suppression resistor to the end of the sparkplug lead wire and connecting the other end of the radiation suppressionresistor to the spark plug so that the radiation suppression resistor isconnected in series between the spark plug lead wire and spark plug.

4. Structure as set forth in claim 1 wherein the resistor has aninductance of between 30 and 45 microhenries as measured on a TechtronicLC. l30 meter.

5. Structure as set forth in claim 4 wherein the spark plug includes anouter metallic body portion, and an inner ceramic insulator corereceived within the outer body portion, and the first of the lowerelectrodes extends through the insulator core, the second of the lowerelectrodes is secured to the outer body portion in spaced relation tothe first lower electrode, and the spark plug further includes an upperelectrode secured to the insulator core in spaced relation to the firstlower electrode and the wire wound radiation suppression resistor ispositioned within the insulator core and connected at opposite ends tothe first lower electrode and to the upper electrode.

6. Structure as set forth in claim 4, wherein an insulating spark plugboot construction is provided between the spark plug lead wire and thespark plug the wire wound ignition circuit radiation suppressionresistor is positioned within the boot construction which furtherincludes terminals provided within the boot construction for connectingone end of the radiation suppression resistor to the end of the sparkplug lead wire and connecting the other end of the radiation suppressionresistor to the spark plug so that the radiation suppression resistor isconnected in series between the spark plug lead wire and spark plug.

1. An ignition circuit including a spark plug having a pair of lowerspaced apart electrodes, a spark plug lead wire connected in series withthe spaced apart electrodes of the spark plug, and a wire wound ignitioncircuit radiation suppression resistor connected in series with theseries connected spark plug lead wire and electrodes of the spark plugand positioned closely adjacent the electrodes of the spark plug, whichresistor has an inductance of between 10 and 800 microhenries and aresistance of between 15 and 30 ohms.
 2. Structure as set forth in claim1 wherein the spark plug includes an outer metallic body portion, and aninner ceramic insulator core received within the outer body portion, andthe first of the lower electrodes extends through the insulator core,the second of the lower electrodes is secured to the outer body portionin spaced relation to the first lower electrode, and the spark plugfurther includes an upper electrode secured to the insulator core inspaced relation to the first lower electrode and the wire woundradiation suppression resistor is positioned within the insulator coreand connected at opposite ends to the first lower electrode and to theupper electrode.
 3. Structure as set forth in claim 1, wherein aninsulating spark plug boot construction is provided between the sparkplug lead wire and the spark plug, the wire wound ignition circuitradiation suppression resistor is positioned within the bootconstruction which further includes terminals provided within the bootconstruction for connecting one end of the radiation suppressionresistor to the end of the spark plug lead wire and connecting the otherend of the radiation suppression resistor to the spark plug so that theradiation suppression resistor is connected in series between the sparkplug lead wire and spark plug.
 4. Structure as set forth in claim 1wherein the resistor has an inductance of between 30 and 45 microhenriesas measured on a Techtronic L.C. 130 meter.
 5. Structure as set forth inclaim 4 wherein the spark plug includes an outer metallic body portion,and an inner ceramic insulator core received within the outer bodyportion, and the first of the lower electrodes extends through theinsulator core, the second of the lower electrodes is secured to theouter body portion in spaced relation to the first lower electrode, andthe spark plug further includes an upper electrode secured to theinsulator core in spaced relation to the first lower electrode and thewire wound radiation suppression resistor is positioned within theinsulator core and connected at opposite ends to the first lowerelectrode and to the upper electrode.
 6. Structure as set forth in claim4, wherein an insulating spark plug boot construction is providedbetween the spark plug lead wire and the spark plug, the wire woundignition circuit radiation suppression resistor is positioned within theboot construction which further includes terminals prOvided within theboot construction for connecting one end of the radiation suppressionresistor to the end of the spark plug lead wire and connecting the otherend of the radiation suppression resistor to the spark plug so that theradiation suppression resistor is connected in series between the sparkplug lead wire and spark plug.